Bounds on charged lepton mixing with exotic charged leptons

摘要

We examine the effects of mixing induced light heavy charged lepton neutral currents on the partial wave amplitude for the process l+l− →ZZ (withl = e,μ or τ). By imposing the constraints that the amplitude should not exceed the perturbative unitarity limit at high energy (√s = Λ), we obtain bounds on light heavy charged lepton mixing parameter sin2(2θ _L a ) where θ _L a is the mixing angle of the ordinary charged lepton with its exotic partner. For Λ = 1 TeV, no bound is obtained on sin2 (2θ _L a ) form _E < 0.69 TeV. However, sin2 (2θ _L a ) ≤ 1.52×10−5 form _E = 5 TeV, sin2 (2θ _L a ) ≤ 2.41 ×10−7 form _E = 10 TeV. Similarity for Λ = ∞ no bound is obtained on sin2 (2θ _L a ) for m_E < 1.97 TeV and sin2 (2θ _L a ) ≤ 0.15 form _E = 5 TeV and sin2 (2θ _L a ) ≤ 3.88×10-2 form _E = 10 TeV.